Pneumonia is an infection of the lung. The lungs fill with fluid and make breathing difficult. Pneumonia disproportionately affects the young, the elderly, and the immunocompromised. Pneumonia is the world’s leading cause of death among children under 5 years of age, accounting for 15% of all deaths of children under 5 years old, killing approximately 2,200 children a day in 2017.
In the US, pneumonia is less often fatal for children, but it is still a big problem. Pneumonia is the number one most common reason for US children to be hospitalized. For US adults, pneumonia is the most common cause of hospital admissions other than women giving birth. About 1 million adults in the US seek care in a hospital due to pneumonia every year, and 50,000 die from this disease.
Pneumonia can be caused by lots of different types of microbes, and no single one is responsible for as many as 10% of pneumonia cases. The most common organisms are viruses and bacteria. But for most pneumonia patients, the microbe causing the infection is never identified.
Pneumonia is diagnosed based on medical history and clinical symptoms of fever, chills, cough (usually with phlegm), shortness of breath and sometimes chest pain when breathing or coughing. Some may have nausea, vomiting, and diarrhea. Physical exams will be conducted to listen to the lungs for abnormalities and pulse oximetry or blood oxygen level test will be done to see how much oxygen is in the blood. Additional tests could be done that include a chest X-ray, blood test for complete blood count (CBC) to check for white blood cells that fight infections, nasal swabs to check for viruses, sputum samples to check for bacteria, and maybe blood culture to see if the bacteria have spread to the blood stream.
Pneumonia can cause lung injury or acute respiratory distress syndrome (ARDS) where some patients may require the mechanical ventilator to support their breathing. Pneumonia is also the most common cause of sepsis and septic shock, causing 50% of all episodes.
Antibiotics can be effective for many of the bacteria that cause pneumonia. For viral causes of pneumonia, antibiotics are ineffective and should not be used. There are few or no treatments for most viral causes of pneumonia. We need to be careful with the overuse and misuse of antibiotics when we treat pneumonia that are not due to bacteria to prevent antibiotic resistance.
Pneumonia can be prevented by immunization, adequate nutrition, and by addressing environmental factors. Vaccines are available for some but not many causes of pneumonia. For example, influenza virus vaccines are effective for the strains circulating that year and should be taken every year. The pneumococcal bacterial pneumonia vaccines are recommended for higher risk groups such as children, the elderly and those with immunocompromised states).
While successful pneumonia treatment often leads to full recovery, it can have longer term consequences. Children who survive pneumonia have increased risk for chronic lung diseases. Adults who survive pneumonia may have worsened exercise ability, cardiovascular disease, cognitive decline, and quality of life for months or years.
The importance of pneumonia is highlighted by the emergence of the current COVID-19 pandemic that has so far has affected more than 65 million people around the world (December 2020). More information is being discovered about the virus SARS-CoV-2 (that causes COVID-19) when it comes to how this virus causes disease, how to prevent transmissions, how to treat with medications, and how to be protected with new vaccines.
